[Arran]

I was not refering to the overall thickness of the plywood used in the grill but the thickness of the laminations. I have managed to pick up some Baltic Birch plywood, of 3/8'' thickness, they also have some in 1/8, 1/4, and 5/8'' thickness, 3/8'' and full 1/4'' seems to have been the most popular stuff used in old radio cabinets and furniture? If you can't get the Baltic Birch you can use Douglas Fir plywood of a decent grade. The problem with most cabinet plywoods is that they often have a poplar or a luan core, which is soft, and they are nominally sized.
Regards
Arran